The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In diagnostic systems for electrically controlled devices employing electric motors or other actuators it can be difficult to tell the exact cause of an error condition by examining system-generated error codes alone. For example, in vehicular systems, such as automotive systems, it is common to employ control modules that record a predetermined error code upon detecting a predefined error condition. Mechanics can then review these recorded error codes as part of the diagnostic procedure. The problem with such error codes is twofold. First, available memory space and processing power is limited. Thus most systems must suffice with only a finite and often small number of recognized error conditions. Second, some error conditions are intermittent. Thus the mechanic may not be able to reproduce the reported error condition, making it difficult to discern what the cause may have been.
In electrically controlled systems employing electric motors or other electric actuators, knowing the motor or actuator current at the time an error condition occurred would be a valuable diagnostic aide in discerning the cause of the error. Unfortunately, conventional techniques for measuring current are not often practical in vehicular or automotive applications where cost, weight and system complexity must be minimized. For example, conventional techniques, such as employing a precision shunt resistor in the current path, or use of a Hall-Effect sensor to detect current flow both require an analog-to-digital convertor to convert the measured analog current value into a digital value suitable for storing in the diagnostic memory of the control module. Precision shunt resistors and Hall-Effect sensors, and the associated analog-to-digital convertors add cost, weight and complexity (more parts to fail).